An international team of researchers from the U.S., England, and Sweden pieced together evidence from the plant fossil record and ecology of ancient and modern birds, in order to conduct the study. The lead author is Daniel Field, of the Milner Centre for Evolution at the University of Bath.

Gauthier said the study’s hypothesis explains the disappearance of the common tree-dwelling birds of the Cretaceous period. “It also explains the fact that although many birds live in trees today, their earliest relatives emerging from the wake of the asteroid impact were long-legged ground dwellers,” he said.

Additional co-authors of the study are Antoine Bercovici of the Smithsonian Institution, Jacob Berv of the Cornell Lab of Ornithology, Regan Dunn of the Field Museum of Natural History, Tyler Lyson of the Denver Museum of Nature and Science, David Fastovsky of the University of Rhode Island, and Vivi Vajda of the Swedish Museum of Natural History.